To meet the increasing demand of future mobile communication systems for system capacity, spectrum utilization, and data transmission rate, etc., in the existing LTE (Long Term Evolution) standard, MIMO (Multiple Input Multiple Output) technique and OFDM (Orthogonal Frequency Division Multiplexing) technique are employed. Wherein, the MIMO technique can double or even triple the system capacity and spectrum utilization without increasing the bandwidth. On the other hand, the OFDM technique is a typical technique applied in wideband transmission, and it has many advantages, including high resistance to multi-path fading, insensitivity to narrow-band interference and noise, and flexible bandwidth expansion, etc.
In wireless communication systems, the coherent detection technique is currently employed to achieve better receiving performance. Since channel parameters must be obtained to accomplish coherent detection, the channel estimation must be performed at the receiving end. In order to estimate the channel parameters timely and accurately, a pilot symbol assisted channel estimation method is currently employed in the actual communication systems. In MIMO systems, the multiple channel parameters must be estimated for each receiving channel; In OFDM systems, the channel parameter to be estimated usually indicates the frequency response parameter of channel.
There are a variety of channel estimation methods for MIMO systems which employ code division pilot on the same time-frequency resource. In the existing channel estimation methods, the accurate estimation of channel parameters always involves the complex matrix operations, such as large-dimension matrix inversion; such complex matrix operations will bring huge load on the entire communication system and degrade the processing speed of the system. To solve the above problems, the present invention proposes a channel estimation method, which utilizes polyphase extraction and decorrelation methods to reduce the order of complexity in the implementation of the MIMO channel estimation method, and the discrete cosine transform and filtering methods are employed for interpolation after polyphase extraction so as to improve the accuracy of the MIMO channel estimation method.